This invention relates to a needle plate for a double needle bar loop pile tufting machine, and more particularly to a needle plate having needle plate fingers adequate to support the base fabric for penetration by both rows of needles.
In a conventional multiple needle tufting machine, the needle plate is provided with a plurality of uniformly spaced straight fingers extending from one edge of the needle plate in the direction of fabric feed, or rearward, so that each finger extends between and beyond an adjacent pair of needles. These fingers are adapted to provide a support for the portion of the base fabric in the path of the needles and are spaced to permit free reciprocation of the needles between the fingers. In a conventional multiple needle tufting machine, the needle plate fingers are uniformly spaced at the same gauge as the needles.
Furthermore, a conventional needle plate finger has a rectangular cross-section, with its short dimension transverse, and its long dimension vertical. Thus, each cantilevered needle plate finger has substantial depth to provide sufficient strength to support the base fabric as the fabric is penetrated by the needles. Moreover, the short transverse dimension of each needle plate finger is desirable so that the needles can be spaced closer together to achieve finer gauges.
The above described conventional needle plates are quite adequate for supporting base fabric moving through a multiple needle tufting machine in which the needles are in-line, that is, in a single transverse row or line, and also where the needle gauge is not too narrow or fine.
It is well established in the art of tufting to reduce the needle gauge by staggering the needles, that is, to position a transverse row of rear needles behind a transverse row of front needles and to offset transversely the rear needles relative to the front needles. Various needle plates have been designed particularly for supporting the base fabric as it moves through a staggered needle machine. Examples of such needle plates are shown in the following U.S. Pat. Nos.
2,975,736, J. L. Card, Mar. 21, 1961 PA0 2,976,829, R. T. Card, Mar. 28, 1961 PA0 3,398,708, R. T. Card, Aug. 27, 1968 PA0 3,641,956, Ownbey, Feb. 15, 1972 PA0 4,503,787, Watkins, Mar. 12, 1985 PA0 4,658,739, Watkins, Apr. 21, 1987 PA0 2,889,791, Fedevich, June 9, 1959 PA0 3,025,807, Gebert, Mar. 20, 1962
The following U.S. patents disclose multiple needle tufting machines in which the needles in the front row and the needles in the back row are longitudinally aligned: U.S. Pat. Nos.
In both of the above patents, the base fabric is supported over a long span beneath two transverse rows of needles by a plurality of transversely spaced elongated, straight grating bars, which are supported at both their front and rear ends and in which a grating bar extends between each pair of adjacent needles.
In all of the above patents, it will be noted, that there is a needle plate finger extending between every adjacent pair of needles. Thus, the thickness or transverse dimension of each needle finger limits the proximity of spacing of the needles, and therefore the needle gauge.
In the applicant's U.S. patent application Ser. No. 150,759, filed Feb. 1, 1988, for "DOUBLE NEEDLE BAR LOOP PILE TUFTING APPARATUS", FIGS. 10 and 11 disclose transverse rows of front and rear needles and hook bars. In this apparatus a conventional needle plate having relatively short fingers is utilized for supporting the base fabric beneath the front needles, but separate needle plate fingers are affixed to the rear hooks for supporting the base fabric as it passes beneath the rear needles. Although these needle plate fingers affixed to the rear hooks have worked satisfactorily, nevertheless, there are some disadvantages. In order to vary the pile height in a conventional tufting machine, it is necessary to raise and lower the bedplate supporting the needle plate in order to vary the distance between the plane of the base fabric and the bottom of the looper, which determines the pile height, unless back-robbing is involved. Therefore, when the needle plate is utilized only for the front needles, as disclosed in FIG. 10 of the Watkins application Ser. No. 150,759, the rear needle plate fingers affixed to their corresponding rear hooks predetermines the pile height and permits no means of varying the pile height. Moreover, because of the longitudinal spacing between the front needle plate fingers and the rear moving needle plate fingers, the rear fingers occasionally interfere with the passage of the front loops as they move rearwardly with the base fabric.